Sunday, 26 January 2014

The Humber Speedster Project - Update #1

I realized after mocking up the body in cardboard that I need to have the seat finished to be able to position in and get the right curve line for the side entry.  Easy ! I’ll just knock up the seat frame and get it upholstered later.  On reflection I found it wasn’t so easy - building a seat frame that will allow for the upholstery thickness, then be in the correct position on the car so I can reach, and have full depression travel of the clutch pedal AND be comfortable, AND be fairly snug, (remember there are no sides or roof on this car, so one will need some feeling of security!) Therefore the depth of the seat must be correct, the height of the seat must be correct, the height of the sides and back rest must be correct.  Are you getting the picture?!
I’ll have to admit it was really testing me…..where to begin, where to begin?  So I began by making the base by gluing together two sheets of 17 mm form ply, this would give it a good strong base, cut to fit the shape of the rear of the body. After this point I really only had a vague idea. OK, well I can't procrastinate any longer... I decided to cut the side panels, install them, then work out what to do from there ;-)  I marked out the coordinates on a sheet of form ply then ask my darling, talented and artistic wife to help me with the curvature of the sides. (I had a basic idea from looking at many, many pictures on the net of other Speedster seats, but just wasn’t sure of the right one to suit the previous requirements, and aesthetics).  I taped an electrical lead across the lines I’d drawn, then stood back – Svenja looked, then said try that curve there, that one a little deeper here, and Voila, a shape is borne!
Out came the trusty jig saw, (oh, by the way if anyone knows how to get these little buggers to cut a straight vertical cut let me know, will you? ;-) The shape was cut and tested on my son sitting in the ‘estimated’ right position – looked good to me. The shape was transferred to the other side and cut again. I had a little heart attack when I thought I’d cut it wrong then realized it’s a 3D shape - the rear curve goes inwards behind the occupants back/shoulder.
Kerfing; the trick to get wood to bend on slow or fast angles.   I made saw cuts ½” (12mm) apart, about a millimeter under the outter surface, about 12 in 6” or 150mm. These allowed me to mold the ply to the curve, with curved blocks behind them to keep them in place. A couple of the ‘Kerfs’ did break by my rough handling, so I taped them up and continued, these won’t be seen so it’s no biggie. 

The 1st side in place.

Kerfing detail

LHS rear section added.

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